1. Field of the Invention
The invention relates to a nasal mask for use in the delivery of Non-invasive Positive Pressure Ventilation (NPPV) and for nasal continuous positive airway pressure (nasal CPAP) therapy of sleep disordered breathing (SDB) conditions such as obstructive sleep apnea (OSA).
2. Background of the Invention
The application of nCPAP for treatment of OSA was taught by Sullivan in U.S. Pat. No. 4,944,310, incorporated herein by reference in its entirety. In nCPAP treatment of OSA, pressurized air or other breathable gas is provided to the entrance of a patient's airways at a pressure elevated above atmospheric pressure, typically in the range 4 to 20 cm H20 to “splint” open the patient's upper airways and prevent apneas.
Apparatus to deliver nasal CPAP and NPPV therapy typically comprises a blower, an air delivery conduit and a patient interface. The blower may be programmed to deliver a range of different forms of therapy. In one form, a constant pressure of air or breathable gas is provided to the patient. It is also known for the level of treatment pressure to vary from breath to breath in accordance with patient need, that form of treatment being known as automatically adjusting nasal CPAP treatment as described in U.S. Pat. No. 5,245,995 (Sullivan and Lynch), incorporated herein by reference in its entirety. NPPV is another form of treatment for breathing disorders. In its most basic form, a relatively higher pressure of gas may be provided in the patient mask during the inspiratory phase o f respiration and a relatively lower pressure or atmospheric pressure being provided in the patient mask during the expiratory phase of respiration. In other modes, the pressure can be made to vary in a complex manner throughout the respiratory cycle. For example, the pressure at the mask during inspiration or expiration can be varied through the period of treatment. See, for example, U.S. Pat. No. 5,704,345 and International Patent Publication Nos. W098/12965 and W099/61088, all of which are incorporated by reference herein in their entireties. In this specification, the term NPPV therapy will be used to describe all these forms of NPPV and nasal CPAP therapy.
The patient interface for NPPV therapy may take many forms, such as a nasal mask assembly, a nose and mouth mask assembly, nasal cushions or a nasal prongs or pillows assembly. A mask assembly typically includes a rigid shell, a soft face-contacting cushion, a forehead support and headgear for securing the mask to the head.
In one known mask assembly, the headgear includes a cap portion with four straps. In use, the cap portion engages the occipital portion of the patient. Furthermore, in use, the two lower straps extend between the cap portion and a nasal mask while the two upper straps extend between the cap portion and a forehead support. See, for example, U.S. Pat. No. 6,119,693 (Kwok, Matchett and Grant), incorporated herein by reference in its entirety.
Some patient interfaces include quick or convenient release mechanisms for enabling a patient and/or clinician to disengage from the blower, blower tube and/or the mask/headgear assembly. Quick or convenient release mechanisms are useful where NPPV therapy needs to be temporarily interrupted or where a system failure causes a cessation of gas flow to the patient interface. For example, as disclosed in U.S. patent application Ser. No. 09/482,718, incorporated herein by reference in its entirety, the headgear and mask can be removed from the patient by pulling a conveniently located cord to decouple hook and loop fasteners between engaging headstraps that are positioned, for example, at the rear of the headgear assembly. In another example, as disclosed in U.S. patent application Ser. No. 09/504,220, incorporated herein by reference in its entirety, the headgear/mask assembly can be removed from the patient by detaching a connector member for the headstrap, which connector member is connected directly to the frame of the mask. See also U.S. Pat. No. 3,990,727, which discloses a quick detachable coupler that appears to be employed by the SleepNet™ IQTM mask.
Since the patient must be able to sleep while wearing the patient interface, it is desirable that it be comfortable. In addition, the patient interface should provide a good seal to prevent or reduce leaks, or to better control any leak that occurs and to maintain efficacy of treatment. Since the shape of people's noses, faces and heads vary widely, from a commercial perspective, it is important to be able to manufacture patient interfaces which can accommodate this range of facial shapes without having to carry excessive inventory through a large number of sizes. A number of patient interfaces have been designed with the goals of patient comfort, ease of use, adjustability and the ability to accommodate a wide range of patient face and head shapes in mind.
U.S. Pat. No. 5,243,971 (Sullivan and Bruderer) provides a patient interface (both nasal and full-face masks) that is suitable for use in NPPV therapy. The mask has a face contacting portion mounted to a shell which is sized and shaped to overfit the nose region of an intended wearer, and the face contacting portion is in the form of a distendable membrane which is molded from an elastic material. U.S. Pat. No. 5,243,971 is hereby incorporated by reference in its entirety.
U.S. Pat. Nos. 6,357,441 and 6,112,746 (Kwok and Styles) each describe a nasal cushion which comprises a substantially triangularly shaped frame from which extends a membrane. These patents are hereby incorporated by reference in their entirety.
Other nasal masks are disclosed in U.S. Pat. Nos. 5,724,965 and 6,119,694, incorporated by reference in their entirety. Each describes a nasal cushion that engages with the tip of the nose or that portion of the nose in the horizontal plane just above the upper lip of the patient. In PCT/US00/11329 (WO 00/69521), incorporated by reference in its entirety, a triangular-shaped nasal cushion includes a tapered profile that narrows towards the face of the patient. Some of these prior art masks/cushions has experienced significant challenges from the perspective of patient comfort, potential nasal vent occlusion, stability and/or sealing (especially at the nasal bridge and cheek regions).
A number of adjustable forehead supports have been developed with the aim of achieving a serviceable seal while increasing patient comfort and accommodating the greatest number of patients in the population. For example, U.S. Pat. No. 6,119,693 (Kwok, Matchett and Grant) describes an adjustable forehead support for a nasal mask or full-face mask. The forehead support may be adjusted for the different shapes and sizes of a facial profile. The angle of the seal relative to the face may be adjusted with this invention. U.S. Pat. No. 6,119,693 is hereby incorporated by cross-reference in their entirety. In International Patent Application PCT/AU00/00097 (WO 00/78384), a forehead support is disclosed that is adapted to be secured to a respiratory mask. International Patent Application PCT/AU00/00097 (WO 00/78384) is hereby incorporated by cross-reference in its entirety.
Accordingly, a need has developed in the art to provide a mask assembly that is capable of overcoming the drawbacks or limitations of the prior art.